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"Medical Journeys" is a set of clinical resources reviewed by physicians, meant for the medical team as well as the patients they serve. Each episode of this 12-part journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.

What caused a healthy 39-year-old woman to develop a painful discolored mass with a brownish discharge along the edge of her cesarean scar?

As Minakshi Sardha Singh, MD, of Inova Fairfax Women's Hospital Medical Campus in Virginia, and colleagues described in the , the 3-cm lump started to develop about a year and a half previously, soon after early labor had necessitated an emergency cesarean.

The authors explained that because of the complicated preterm breech labor and the unformed lower uterine segment, the team used an "inverted T" incision. The birth of the infant was followed by an uneventful hospital stay, and postpartum follow-up at 6 weeks revealed nothing unusual.

About 4 months after the surgery, the patient said she began to have constant pain at the site of the scar, which was also tender to the touch. She estimated the pain as usually 3 out of 10 on the pain scale, but the pain increased to about 6 out of 10 when she was menstruating. She said that for the past several months, the pain had followed a monthly cyclic pattern and was often accompanied by a discharge of bloody fluid from the incision site.

"Physical examination revealed a non-mobile, nodular, moderately pigmented area of approximately 2×3 cm at the incision's left lateral border. Palpation of the mass exhibited exquisite point tenderness," the authors said.

They ruled out several differential diagnoses, including an infection or abscess at the scar site, and stitch granuloma, before settling on cutaneous endometrioma as the most likely diagnosis.

The team then ordered a trans-abdominal soft-tissue ultrasound using a linear high-frequency transducer with color Doppler evaluation. This showed an irregular hypoechoic solid mass of 2×1.3×2.2 cm that was projecting into subcutaneous tissues. The imaging revealed internal vascularity in the area that was tender on palpation.

"We planned to explore and resect the abdominal mass to confirm cutaneous endometriosis," Singh and co-authors noted, adding that there was a large area of fibrotic tissue surrounding the scar, which they excised completely, along with the nodular portion, which was sent to the lab for examination.

The histopathology report noted "endometriosis involving fibro-adipose tissue with dense fibrous scarring," and a hematoxylin and eosin photomicrograph showed "tissue surrounding benign endometrial glands and stroma consistent with endometriosis, showing hemorrhage at the center of the cystic space."

The findings confirmed the presumed diagnosis, so molecular biology testing was deemed unnecessary. The team noted, however, that such tests can identify increases in both estrogen receptor activity and local growth factors, and along with anti-CD 10 staining, "can better demonstrate cutaneous endometriosis in the proliferative phase."

The stitch line healed without any complications, and as of the time of the case report, the patient remained in follow-up and there had been no recurrence for at least 5 months.

Discussion

Endometriosis is a chronic pathological condition in which endometrial tissue becomes implanted outside the uterus; most often, this occurs in the ovaries or fallopian tubes, but the condition can occur anywhere in the body.

When the tissue implants in the skin, it is referred to as "cutaneous endometriosis," and categorized as primary or secondary. Primary means it occurs in the absence of any history of endometriosis; secondary cutaneous endometriosis, also referred to as scar endometriosis, occurs after a surgery.

Cutaneous endometriosis generally involves an abdominal mass that is not malignant, pain that recurs with menstruation, and a history of abdominal surgery. "The degree of pain and dimensions of scar endometriosis vary with the menstrual cycle," with symptoms typically presenting approximately 3.7 to 4.5 years after a cesarean section, Singh and co-authors noted.

Risk factors for abdominal wall endometriosis include low body mass index (BMI), nulliparity, starting menstruation at a young age, having a late menopause, and having a first-degree family history of endometriosis.

Abdominal wall endometriosis tends to cause more cyclic pain in patients who have had more live births and have a higher BMI. The patient in the case report, however, had delivered two children and had an average BMI.

Singh and co-authors pointed to several theories about how endometriosis develops, including the metaplasia theory, the embryonic rest theory, and the transport theory. This patient may have developed cutaneous endometriosis due to "iatrogenic implantation of endometrial tissue that escaped through an emergency cesarean incision and seeded into the edge of the corresponding abdominal wall," the team wrote.

"Careful history taking and a diligent examination supported by conventional imaging are pivotal for preoperative diagnosis," and ultimately, pathology provides the definitive diagnosis, the authors stated.

The unspecific presentation of scar endometriosis makes it challenging to distinguish between several differential diagnoses, such as "keloid, hematoma, desmoid tumor, lymphadenopathy, and benign (neuroma) and malignant growths (melanoma)," the case authors wrote.

In addition, they said, while there is a wide range of diagnostic approaches, the usual non-invasive methods such as ultrasound with or without color Doppler, CT scans, and MRI tend to be inconclusive for many reasons. One promising non-invasive cost-effective diagnostic approach, the authors added, is dermoscopy.

cytology, while invasive, represents a valuable and economical technique, the team said, citing a small study of the modality in seven patients. The use in diagnosing , however, is controversial, due to "the potential for nucleation of the endometriotic tissue in new areas."

Surgical excision, though, remains the most effective means of diagnosing , and as a treatment, it has a low recurrence rate – just 9% in one study of 33 women, the case authors wrote. "Excision should include standard tissue 1 cm away from the solid endometriotic tissue and may require the use of a polypropylene mesh to prevent incisional hernia."

Noting the increasing rate of cesarean sections, Singh and co-authors suggested some simple measures to help scar endometriosis:

• Quick removal of swabs from the surgical site to prevent inoculation of the endometriotic tissue

• Use of abdominal compresses as a physical barrier to protect the surgical margins from the uterine cavity

• No reuse of tools employed earlier in the surgery, such as needle holders and forceps, and suture materials, when closing layers of the abdominal wall

• Vigorous irrigation of the incisional site with a high saline jet prior to abdominal closure to ensure clearing of all dead subcutaneous space

Given the increasing odds of encountering cutaneous endometriosis, "education to raise awareness among obstetricians is required to prevent cutaneous endometriosis," the team concluded.

Read previous installments of this series:

Part 1: Endometriosis: Understanding the Pathogenesis and Pathophysiology

Part 2: Diagnosing Endometriosis

Part 3: Managing Endometriosis: Research and Recommendations